To date, most recombinant protein-based pharmaceuticals for human use have been produced using non-human mammalian cells, for example, Chinese hamster ovary (CHO) cells, mouse melanoma (NSO) cells, and mouse myeloma (SP2/0) cells. There have been attempts to use human cell lines for the production of therapeutic recombinant proteins, for example, the production of active protein C using human embryonic kidney 293 cells (Eli Lylly, 2001), the production of interferon-beta using Namalwa cells (Wellcome Research Laboratory, 1999), the production of truncated recombinant factor VIII and a variety of antibodies by HKB11 cells (Cho et al., 2003, Biotech. Prog 19:229-232), and the production of a variety of antibodies and virus DNA by PER.C6 cells (Fallaux et al., 1998, Human Gene Therapy, 9:1909-1917) (Jones et al., 2003, Biotechnol. Prog. 19:163-168 and Xie et al., 2003, Biotech. Bioeng. 83:45-52).
Korean Patent No. 627,753 discloses the use of human host cells, HKB11 cells to produce proteins which are difficult to express in CHO cells (Cho et al., 2003, Biotech. Prog 19:229-232) (Cho and Chan, 2002, Biomedical Science 9:631-638 and U.S. Pat. No. 6,136,599). Korean Patent No. 616,028 discloses a method of producing truncated recombinant factor VIII by HKB11 cells. The HKB cell is a cell line derived from HH514-16 and includes a genome of Epstein Barr virus (EBV) which is deficient in B-cell immobilization and virus production (Rabson et al., 1983, PNAS USA 87:3660-3664). The HKB cells show characteristics such as high-density growth, high transfection efficiency, and simple MTX-induced amplification, massive secretion of target proteins, and extinction of IgM expression, which are suitable for producing therapeutic proteins. However, it was found that EBV tended to be isolated from the HKB cell during the cultivation of the HKB cell (Chang et al., 2002, J. Virol. 76:3168-3178). This tendency indicates that the HKB cell may become devoid of EBV, thereby failing to preserve various beneficial properties for effective expression of heterologous genes. That is, the HKB cell loses EBV when cultured for a long period of time, so that therapeutic recombinant proteins may not be produced.
Since a EBV genome does not exist as episomes but is inserted into chromosomes in Namalwa cells (Matsuo et al., Science 14 Dec. 1984: 1322-1325, Henderson et al., 1983, PNAS USA 80: 1987-1991 and Rose et al., 2002, J. Clin. Microbiol. 40:2533-2544), the inventors have developed a novel human host cell line which retains EBV-derived features without virus production, using Namalwa cells.